Homeostasis in the Human Body

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Transcript of Homeostasis in the Human Body

The Excretory SystemThe excretory system uses the kidneys to maintain homeostasis by:

Filtering water and salt from the bloodRegulating the body's water contentEliminating toxic by-products from the bodyRegulating ion concentrationsFeedback MechanismsHomeostasis is maintained using positive or negative

feedback mechanisms. In the endocrine system, most glands are under negative feedback influence. Some Control Mechanisms Involved in Homeoestasis 1. Sensor: A monitor in/on an organ that detect changes in external conditions (such as nerve endings on the skin).

2. Coordinating Center: (Hypothalamus or brain stem) Receives and interprets information from a sensor and sends it to the designated effector .

3. Effector: (Gland or organ) Carries out the appropriate response to restore the homeostatic balance.

4. Negative Feedback Loops: Where a change in environment triggers a control mechanism to respond accordingly (this is covered in more detail shortly).Homeostasis inthe Human Body- The Pituitary gland (endocrine) releases anti diuretic hormone (ADH) to encourage more water re absorption by the kidneys (excretory) when the body needs to keep water within it.

- The hormone aldosterone is released by the adrenal glands (endocrine) to aid blood pressure regulation (excretory).

- The enzyme renin is released to activate hormone angiotensin (endocrine) to increase blood pressure (excretory).

- The excretory system is responsible for a buffer reaction that creates more bicarbonate (base) and excretes protons

(acid) in urine to maintain

pH balance in the body.Positive Feedback MechanismsAlthough most endocrine glands use negative feedback to induce a response, some use positive feedback instead. Positive feedback mechanisms control events that do not require constant adjustment, and instead of attempting to maintain hormone levels within narrow ranges, it promotes deviation from the normal value.Homeostasis is the body's abilityto maintain a constant internalenvironment, despite external changes. To the right is anoverview of how homeostasisworks.

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Using these control mechanisms, the body systems are able to communicate and respond to one another to maintain a homeostatic balance.How is the excretory system related to others in homeostasis?The Excretory System works with the Endocrine System by using hormones to regulate homeostasis:The Endocrine SystemThe endocrine system uses chemical messengers called hormones to make regulatory changes in the body. It is composed of glands that release these hormones into the blood stream, which delivers them to their target cells. The release of these hormones increases or decreases the target cell's activity, therefore maintaining homeostasis in the body. The image at the right shows the glands of the endocrine system.The endocrine system is the body's main way of maintaining homeostasis. The pituitary gland is the "master gland" of the endocrine system as it controls most other glands in this system. It works in conjunction with the hypothalamus of the nervous system; the hypothalamus sends a message to the pituitary, and the pituitary gland then releases the necessary hormone(s) or sends a signal to the appropriate gland to do so.Negative feedback is similar to a thermostat in a house. When the temperature reaches a certain degree, the heat turns on/off. This is to save energy, and the same goes for the body.A homeostatic example of this would be calcium level regulation - if it is detected that there is too little calcium in the blood, parathyroid hormone (which regulates blood-calcium levels) is released to stimulate calcium to be released from the bones. This feedback loop is shown to the left.An example of positive feedback mechanisms can be seen in child birth. The hormone oxytocin is released to increase the effectiveness of uterine contractions during labor. When the baby is in the birth canal, oxytocin is released which then stimulates stronger contractions (this is positive feedback) to help aid in the delivery of the baby. When the baby is delivered, oxytocin production ends.Homeostasis is a complex and intricate system that we are only just beginning to understand. The topics covered in this presentation are merely scratching the surface of homeostasis - there are other systems involved in homeostatic maintenance, the hormones involved in the endocrine system are vast, and the interconnection of it all makes us appreciate these unconscious processes!In ConclusionHomeostasis ExamplesUnconsciously, the body maintains its own stable environment according to internal and external changes.